In the U.S., climate change is likely to increase average daily temperatures and the frequency of heat waves. Dairy cows are particularly sensitive to heat stress and, according to a new USDA study, by 2030, milk production will have lowered to the point that additional economic costs will exceed $100 million per year.

Heat stress causes changes in respiration, heart rate, sweating, blood chemistry and hormones. It can also alter the metabolism of minerals and water and the digestion of nutrients. Dairy cows are particularly sensitive to heat stress; higher temperatures lower milk output as well as its fat, solids, lactose, and protein content. There's also a decline in cow fertility.

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Looking at the most recent numbers, the USDA study found that heat stress already lowers the value of annual milk production for the average dairy producer by about $39,000, which is equivalent to $1.2 billion in lost production for the entire dairy sector.

Next, the researchers applied five years of contemporary data to four different global climate change models to provide a range of predicted heat loads across U.S. regions in the year 2030. Depending on which climate change model they used, they estimated that milk production for the average dairy would decrease by an additional 0.60 to 1.35%. Southern states would be the hardest hit, with an average decrease of 2%.

In theory, less milk would mean higher prices. Still the dairy industry would be worse off, because of their higher production costs, such as increased energy use for cooling systems. Consumers would also be worse off because they'd face higher milk prices.

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So, the final total? Consumer welfare would drop an additional $64 to $162 million, while producer welfare would decline by an additional $42 to $108 million.

But, according to the USDA:

Because climate change occurs gradually, it should be possible to mitigate some of the negative consequences for livestock production through research into and development of adaptive technologies and practices. Possible innovations to address climate change-induced heat stress include more energy-efficient cooling for animal housing, improved heat tolerant breeds, and improvements in scientific knowledge about the interactions between feed, nutrition, and heat stress.

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Otherwise, the question, "Got Milk?" could begin to take on a more urgent meaning.